snomuncher

Today my stock Z51 A8 with 200 miles on it developed an intermittent shudder every few seconds while driving at 60 mph on the highway. It became more frequent and I pulled off the highway, where the engine began to stumble badly (almost stalling) and the Check Engine light started flashing, the Stabilty Control light came on steady, and the DIC displayed both Service Rear Axle and Service Stabiltrack messages. I was able to crawl home, not exceeding 35 mph. After a few hours I restarted the engine and all the lights and messages remained the same, and the engine idled roughly.

Before calling the dealer to make a service appointment, does anyone have any similar experience or insight that I can provide as possible causes and solutions?

Thanks in advance.

Maxie2U

With only 200 miles it's best to limp it into the dealer if it's close enough to have it looked at. If it was me I would call OnStar and have them arrange to have it flat-bedded to the dealer.

Keep us updated.

djnice

Others have posted these issues. Common causes are loose spark plug wire or bad chassis control module.

snomuncher

Thank you, I did check that the plug wires and ignition coil connectors were all tight.

djnice

Try searching google for some of your symptoms...rough idle, service stabilitrack, etc.

https://www.corvetteforum.com/forums...rear-axle.html

https://www.corvetteforum.com/forums...misfiring.html

https://www.corvetteforum.com/forums...ode-p050d.html

RickHoppe

I would put money on the chasis control module. Had similar symptoms with my 17 GS.

snomuncher

Update:

The problem was solved with the replacement of one spark plug and one spark plug wire on one cylinder. The car displayed a DTC P0330 (engine misfire) which was subsequently isolated to that one cylinder.

As noted elsewhere, the engine misfire induced the service rear axle and service stability system error messages, but there were no faults in either.

djnice

Thanks for following up. I find many threads where the OP never comes back to tell the resolution. I was thinking, maybe only checking for looseness of wires was not going far enough. So good to know that was the case here.

NSC5

Like djnice I applaud your follow up because so many times a search on the internet reveals the same problem but the OP never posts the outcome/resolution.

A flashing CEL almost always indicates one or more cylinders misfiring so it makes sense that it was cured by replacing those parts of the ignition system. A flashing rather than steady CEL is used for these situations to get the driver's attention because sustained misfiring can result in severely overheated catalytic converters and a fire because raw fuel is being dumped into the cats.

In a similar vein, the startup "bark" and initial much louder cold idle you get from the C7 is partially due to the severely retarded timing used during cold start which provides poorer in cylinder combustion and more unburned hydrocarbon content in the exhaust stream to help heat up the cats quickly.

Berglebee

Last week I was driving my 2015 Z06 (23K miles) 65 mph down the highway when it began to shake and miss-fire pretty violently and the "service rear axle" and "service stabilitrack" and check engine light came on. I limped home (1.5miles) and checked the forums for other similar issues. I checked the codes and it gave the P0330 - multiple engine misfire and improper air pressure in supercharger errors. It drove like it was only running on 5 cylinders. It was clearly the cylinders misfiring so I check the plugs and wires and all looked normal, with no signs of anything coming lose or in bad condition. Eventually limped over to the nearest dealership and crossed my fingers ( and toes). Dealership called to say that the spring on the intake valve in the #1 cylinder had lost it's tension and would be covered under the 25k mile power train warranty. I later talked directly to the technician at the dealership who made the repair and he said that he opened up the valve cover to see that the spring had actually broken. Runs great again now and my sphincter has relaxed a little. Glad it happened before the 25k mile point!

don7790

Your power train warranty is for 5 years 100k on a 2015. I think it went to 5 year 60k in 2016.

Dcasole

You were lucky …... I was not so lucky , my #2 cylinder valve spring broke while I was driving down the highway at 70 MPH , by the time I could slow down and pull over the retainer let loose and the valve dropped into the cylinder and the ensuing carnage required a new engine …..

Dave

ricmalaz

I had very similar problems while also having the A8 shudder issue at the same time. Once I did the latest fluid flush the shudder was mostly gone but I found the my misfiring problem could induce it. I was monitoring my misfires with a OBD2 bluetooth monitor and was getting lots of misfires on several cylinders with on cylinder having 2-3 times as many as any other. The misfiring was partially improved when I re-gapped my plugs (another complication from my initial super charger installation) Turned out all of the misfiring on all cylinders was finally eliminated when I replaced the single spark plug wire for that cylinder that had the most misfires.

snomuncher

Here’s another update on this misfire issue that I first posted in 2017.

Two weeks ago I pulled the Vette out for a short drive and as soon as it warmed up I experienced an exact repeat of the same conditions as in 2017: a flashing Check Engine light and two DIC error messages: Service Rear Axle and Service Stablilitrak. My scanner showed DTC P0306, misfire on cylinder #6. Following the same logic as the dealer in 2017, supplemented by info from others with similar experience, I replaced both the spark plug and wire on that cylinder. (In 2017, the dealer replaced the plug and wire on cylinder #8 to solve the problem). Initially the misfire disappeared with no error messages, codes or lights, but on a test drive the same symptoms and errors appeared as soon as the car warmed up. As before, I stumbled home at a top speed of 35 mph. Now the scanner posts both a DTC P0302 misfire on cylinder #2 and a random misfire DTC P0300. It’s hard to believe that any of the parts on cylinder #2- the injector, coil, spark plug or wire- have suddenly gone south so this misfire issue might be caused by a different source, but there are no other DTCs. For info, I’m using an OBDLink MX+ scanner with a wide range of diagnostics.

Any other ideas on how I can chase down the actual cause of these misfires? Thanks in advance.

snomuncher

Update 04/05/20:

After replacing all eight spark plugs and wires there are no new misfire DTCs. Neither is there evidence of defects in the parts removed. Resistance values of the removed wires are within spec. Will monitor the condition over the next few drives.

Dcasole

Good luck !

Dave

C5-VERT

FYI I've had a DI injector go bad and cause the same exact issues as above. As well as cracked plugs. Bad wires. Even fuel pump issues. In your case if it still acts up look at the injector on the cylinder thats misfiring.